 The scFv-EGFP fused proteins in all the groups above are of the same molarity. The 
 Mcherry in Background Group and the 9 different Antigen-Mcherry fused proteins in 
 all the groups above are of the same molarity. The origin p185her2/neu ECD and its 8 
mutants (put into the environment after the scFv-eGFP fused protein and the Antigen-
Mcherry fused protein) in the “Competition Groups” and the “Self Competition 
Groups” are of the same molarity.

 If a Key has a proper affinity to the antibody (strong enough to bind to the antibody, 
 but weaker than the origin antigen), there should be: Ebdo> Ebd> Esc>Ec> Ebg. For 
 example, if Mutant No.3 is exactly the “Key” we want, there will be：Ebdo> Ebd(3)> 
 Esc(3)>Ec(3)> Ebg. 

 Besides, if Ebd is very high, almost equals the FRET efficiency of the directly linked 
eGFP-Mcherry fused protein in previous research[4]，which means that the Mcherry 
and the eGFP is very close to each other, then if we replace the eGFP and the Mcherry 
 with a functional protein(an enzyme for example) and its repressor, there is very 
 likely to be a enzyme-repressor interaction (the enzyme will be repressed before the 
 Key meet the origin antigen and begin to leave the antibody ).